FEDEVEL
Platform forum

Tsukuyomi95 , 04-10-2025, 07:18 AM

Hi everyone! Hope you're all doing well 😊

I just found this channel and wanted to ask a few questions. I'm currently designing a custom board using the ESP32-S3 WROOM-1 in Altium, and it's my first time doing something like this.

Here are a few things I’d love your input on:

Can the 5V pin be used as both input and output? If not, how can I make that possible?
(I'm curious too about generating a 5V output not coming from USB , just trying to deepen my understanding here.)

I’ll be adding some sensors to my board. How should I properly manage the voltage levels?
Also, what’s the best advice you can give me to ensure this custom board turns out well?

Can I rely only on the native USB (USB-OTG) for my board for flashing and programming?
Do I still need a USB-to-UART converter? If not, could you explain why?

Thanks a lot in advance! Any help or tips would be really appreciated 🙏

Robert Feranec , 04-10-2025, 07:34 AM

I am not sure which 5V you mean (probably VCC_5V), there is a diode which will prevent 5V flowing back to USB if external power is connected. But still you need to be careful e.g. if your external power supply has lower voltage than USB there may be some "fight" between the powers.

Tsukuyomi95 , 04-10-2025, 08:19 AM

Oh, right , I did add a diode for protection, and I don’t think I need to add a header or jumper cap in this case

Tsukuyomi95 , 04-10-2025, 08:19 AM

Sorry if I wasn’t clear earlier about the 5V, I meant it more like you said: VCC_5V or Vin, like on the older ESP32 boards

QDrives , 04-10-2025, 04:04 PM

I made a design where the USB could be either in host or peripheral mode and get powered from the PC or supply power to a bluetooth module. All on the same USB A connector.

You need both hardware and software capabilities for this.
In a sense it would just swap constantly between host and peripheral.
In peripheral mode, Vbus is an input and you check to see if power is applied.
In host mode, you supply power and see if a device is detected.

QDrives , 04-10-2025, 04:06 PM

"*How should I properly manage the voltage levels?*" -- What voltage levels? Signal or supply? Higher or lower? Analog or digital?

QDrives , 04-10-2025, 04:09 PM

"*Can I rely only on the native USB (USB-OTG) for my board for flashing and programming?*" -- You need to strap the right pins during boot-up.

Tsukuyomi95 , 04-11-2025, 06:47 PM

Thanks for your response! I think I have a better understanding now of what I need to do. And sorry for the late reply, I’ve been a bit busy lately.

If you don’t mind, I have another question:
I'm planning to integrate the OV2640 camera into my custom board. While reviewing the schematics of the ESP32-CAM and ESP32-S3-EYE MB v2.2, I noticed something:

The ESP32-CAM uses 2.8V and 1.2V for the camera power supply

The S3-EYE MB uses 2.8V and 1.5V

However, the OV2640 datasheet specifies compatibility with 2.8V and 1.2V. So I’m a bit confused , why does the S3-EYE board use 1.5V instead of 1.2V? Is there a specific reason for this change?

In your opinion, what's the best voltage setup for the OV2640? And what kind of issues could arise if I supply 1.5V instead of 1.2V?

Thanks again for your help!

QDrives , 04-11-2025, 06:52 PM

Is the 1.5V intended for a 1.2V camera? Or is it designed for another camera system?

Tsukuyomi95 , 04-11-2025, 07:27 PM

well, as you see, they both use the same module Ova2640 :

Tsukuyomi95 , 04-11-2025, 07:28 PM

and this is the shcematics

Tsukuyomi95 , 04-11-2025, 07:28 PM

for S3-EYE MB :

Tsukuyomi95 , 04-11-2025, 07:29 PM

ESP32-CAM :

QDrives , 04-11-2025, 08:29 PM

On the first picture I see RYS - 2640 - M7 and on the second picture I see TY - OV2640-V2.0 So I do not know if it is exactly the same.
Secondly, do you have the schematic section of the regulator of the S3-EYE MB?
What does the datasheet of the OV2640 state on the supply limits?

Tsukuyomi95 , 04-13-2025, 12:47 PM

Well, as I mentioned before, the OV2640 datasheet specifies compatibility with 2.8V and 1.2V. To keep things simple, I’ll just follow what the datasheet recommends. And yeah, thanks again for your help!

QDrives , 04-13-2025, 03:06 PM

"Limits" is something else than "compatibility".
What is the minimum and maximum?

Tsukuyomi95 , 04-13-2025, 05:39 PM

There is not much difference..

Tsukuyomi95 , 04-13-2025, 05:40 PM

And btw do you have any ideas or advice on designing a custom ESP32-based board that’s battery-powered, with charging, protection, and the ability to switch between a 5V input and a 2S lithium battery without damaging the board?

QDrives , 04-13-2025, 08:02 PM

So 1.2V ±5%. That means you cannot supply it with 1.5V.

QDrives , 04-13-2025, 08:04 PM

Yes. Look up OR-ing, OR controllers or ideal diodes.

Tsukuyomi95 , 04-15-2025, 11:40 AM

Is this connected the right way?

QDrives , 04-15-2025, 11:08 PM

Make sure that if you use +5V_VBUS for detection of connection, you add a low enough resistor to counteract the leakage current from the SS24FL diode.

Tsukuyomi95 , 04-16-2025, 05:50 PM

Is 10kΩ typically enough for this kind of USB VBUS detection? like this?

Tsukuyomi95 , 04-16-2025, 05:51 PM

Oh, and I added a switch to power the board on and off, I’m planning to add a bunch of sensors

QDrives , 04-16-2025, 10:16 PM

"*Is 10kΩ typically enough for this kind of USB VBUS detection?*" -- I said a resistive load for the leakage current to prevent wrong "detection".
Is 10k enough -- that depends. Check the curves of the leakage current. This depends on the voltage (lets take 5V) and temperature.
I will let you think for a while...

Tsukuyomi95 , 04-18-2025, 05:51 PM

I checked the SS24FL datasheet. At 5V reverse voltage and room temperature, leakage is pretty low, typically below 1 μA. But in worst-case scenarios (like high temp), it can go up to hundreds of μA or even close to 1 mA. With a 10kΩ pull-down, that could result in a voltage around 1–2V, which could be interpreted as a HIGH. So while 10kΩ might work in many cases, something like 1kΩ–4.7kΩ is safer for reliable detection

QDrives , 04-18-2025, 08:30 PM

Exactly. I do not know what your temperatures could be, so it is best so look at the graphs yourself.

QDrives , 04-18-2025, 08:31 PM

Also note that it is more the typical values in the graph, so give yourself some margin.

Tsukuyomi95 , 04-19-2025, 11:10 AM

Absolutely, that makes sense. Since temperature in my setup could vary depending on enclosure and load, I agree it’s best not to rely solely on typical values. I checked the reverse leakage current vs. temperature graph in the SS24FL datasheet, it rises significantly with temperature. So to be safe, I’ll go with a lower pull-down value like 1kΩ to give myself a good margin, even under worst-case conditions. Thanks for pointing that out!

Robert Feranec , 04-22-2025, 01:43 PM

if you have there the on off switch already, maybe I would consider to use a three pin switch instead and switch between ext and USB

Tsukuyomi95 , 05-05-2025, 09:25 PM

Yes! I really liked your idea honestly, I’ll add this to my board.

Tsukuyomi95 , 05-05-2025, 09:25 PM

By the way, what do you think is the best DC-DC buck converter (switching regulator) to go from 12V down to 3.3V?

Tsukuyomi95 , 05-05-2025, 09:25 PM

I'm planning to add a 12V stepper motor (1.2A rated, up to 2A max) to the board, and I’m still deciding which regulator to use for the logic part in my PCBA.

Tsukuyomi95 , 05-05-2025, 09:25 PM

Thanks a lot for your help!

QDrives , 05-05-2025, 11:28 PM

There is no "**best** DC-DC buck converter". It all depends.
Availability, cost, complexity, mode, control, external control, area, size, voltage limits, current limits, thermal capabilities, internal or external switch, etc.

Robert Feranec , 05-06-2025, 10:25 AM

often it's the one you use in another product ... you have it already tested and you don't have to stock too many types of components. If you have not used one before, then ideally a one which you will be able to buy for a couple of years e.g. use a well known manufacturer for example TI and select from their power supplies

Tsukuyomi95 , 05-06-2025, 11:41 AM

Yeah yeah, ofc you're right, there's no "best" DC-DC buck converter.
I just meant one that would be suitable for my case, reliable, and won’t risk damaging my board.
As I mentioned earlier, my input is 12V, and I need to step down to 3.3V for the logic side, while also powering a 12V stepper motor (1.2A rated, 2A max) separately.
So I’m mainly looking for a safe and efficient regulator that fits those needs without overcomplicating things.

Tsukuyomi95 , 05-06-2025, 11:41 AM

Thanks, that makes a lot of sense now.
I haven’t used a 12V-to-3.3V regulator in a previous project, so I’ll definitely look into a reliable option from a well-known manufacturer like TI, as you suggested.

QDrives , 05-06-2025, 01:55 PM

12V to 3.3V is a simple requirement.
What current do you need on the 3.3V? What current **range** do you need? Can it get to DCM?
**Safe** and **efficient** usually do not co-exist with **without overcomplicating things**.
You can start here: https://webench.ti.com/power-designer/switching-regulator?powerSupply=0
Make sure you can buy the part before going deep into the simulation / fine-tuning.

Tsukuyomi95 , 05-07-2025, 09:37 AM

Got it, thanks! For the 3.3V rail, I need around 0.9A max, maybe 100–200mA idle, so yeah, it might hit DCM sometimes ,no problem as long as it’s stable.
Totally agree, “safe and efficient” without adding complexity is tricky 😅
I’ll check out TI Webench and make sure the part’s available first.

QDrives , 05-07-2025, 04:03 PM

If you might go in to DCM, it might be better to have a current mode controller.